Using Shed as Paint Booth

[Ferrino]

I have a simple 10'x12' shed in my yard, which I would like to periodically use as a paint booth for car parts (catalyzed paints). It's basically one of those Tuff Sheds you see outside Home Depot, with 2x4 open stud walls. There is a sliding window on one end, into which I'd place the intake filters. At the other end, I was planning to locate (down low in a study bay) a hole for a duct leading to one of these explosion-proof fans, which I would locate outside the shed. So a "negative pressure" configuration.

My main question concerns the electrical system and lighting. This shed has a 110v electrical system, with multiple outlets in the open stud bays, connected by Romex. I was planning to shut off this power supply, for obvious reasons. But I will need lighting. I currently have these LED fixtures in the ceiling of the shed (approx. 10 feet above the floor). They have a simple 3-prong plug for supply. Could I just pass an extension cord into the shed just for these? Or is there still a significant risk of these lights igniting the vapors from the internal wiring? The 2 alternatives I see are:

1. Replace LED lights with vapor-proof units.
2. Seal off the top of the shed (containing the lights) from the main area, so vapors cannot get to the lights.

Thanks for your feedback.

 

[pb57]

I may get differences of opinions here but I just built a paint booth (34x14) with 20 commercial paint booth lights i found on Craigslist from a booth that closed down. I put in 2 Canarm enclosed motor exhaust fans. (they are reasonably priced) Mine was done correctly but I wouldn't hesitate doing what your doing and feel safe painting in there. As long as you put in a big enough exhaust fan to get the correct air exchange that osha recommends. with a booth that size the fan wouldn't have to be that big. Just google paint booth air exchange and you will find a chart that recommends the required CFM for your size of booth. I have painted many things in my booth and never have any paint or fumes floating around. they are out the door immediately. I built a intake filter system that doesn't take up much room compared to the typical intake systems and if your interested I can post pics here tomorrow to give you an idea. Paul

 

[Ferrino]

I may get differences of opinions here but I just built a paint booth (34x14) with 20 commercial paint booth lights i found on Craigslist from a booth that closed down. I put in 2 Canarm enclosed motor exhaust fans. (they are reasonably priced) Mine was done correctly but I wouldn't hesitate doing what your doing and feel safe painting in there. As long as you put in a big enough exhaust fan to get the correct air exchange that osha recommends. with a booth that size the fan wouldn't have to be that big. Just google paint booth air exchange and you will find a chart that recommends the required CFM for your size of booth. I have painted many things in my booth and never have any paint or fumes floating around. they are out the door immediately. I built a intake filter system that doesn't take up much room compared to the typical intake systems and if your interested I can post pics here tomorrow to give you an idea. Paul

Thanks for your reply!

When you say "I wouldn't hesitate doing what your doing and feel safe painting in there", are you referring to the general design of the booth or are you referring to the idea of using standard LED shop lights (powered from an extension cord passed into the booth)?

The CFM I am still unclear on. I get wildly different numbers, depending on whether I strive for air exchange or air velocity. For exchange, the volume of the booth is approx. 1,000 ft^3. So a 3,000 CFM exhaust fan would give 3 exchanges per min. But for velocity, I would need 9,000 CFM to get the suggested 100 ft/min (I calculated the cross-section of the booth to be 90 ft^2.).

I'm likely over-thinking this for something I will paint in perhaps once per year, but I'd prefer to spend some time getting it right.

What are the CFM ratings of your two Canarm fans on a 34x14 booth, please?

Yes, I'd be interested to see your intake filter setup, if you have a chance to share. The window opening I have available for the intake is 4.7 ft^2 of area. Which is a very small area compared to the cross-section of the booth.

 

[Stuart in MN]

What you do at home is your own business, but strictly speaking the light fixtures for a paint booth need to be explosion proof, not just vapor tight.

 

[58Yeoman]

I live a charmed life, so don't do what I did. I painted numerous VW's, a couple PU's, a full size Ford van, a full size 69 Pontiac and that 58 Chevy in my avatar...in my attached 3 car garage with no special lights. I ran a furnace blower under one of the doors for exhaust. I also had the two barrel wood stove running sometimes to keep it warm in cold weather. I used a half mask with cartridges, but don't remember what they were...I got them from the chemical plant where I worked.

 

[kwb]

What I would do if concerned would be clear plastic over the top of everything- think Dexter kill room.

Light goes through plastic, vapors get managed by fans (positive pressure).

My personal experience has been more like 58Yeoman but I am working in a space about 10x bigger and 24x by volume. I am not usually trying to get show level quality. When I have been more concerned about keeping dirt out I have done the plastic booth thing in a corner but no special air handling.

 

[Ferrino]

Thanks for the tips. I was actually thinking of covering up the exposed stud bays with plastic, to reduce the amount of **** being sucked in through the gaps in the shed siding. Maybe I will put another sheet under the lights too...

 

[pb57]

I wouldn't hesitate on using your LED lights you stated as long as you use the proper exhaust fan. The 3000 CFM number would be correct for yours. They use the end wall surface area when they calculate the CFM rating. My building is actually 36 foot long and 14 wide. I have 2 Canarm 5500 CFM fans. That 3000 CFM fan will take the fumes out fast on your building. I will get pics of my intake system on here tomorrow. I forget what my opening in my booth is for the intake area but is something like 20 inches wide and 80 inches tall. I built a angle iron rectangle frame that holds 12 - 20x20 inch tacky intake filters that have a wire frame. They are cheap on-line. Even if your system uses less intake filters it would still work good. You would just have to change them more often. I have seen many garage paint booths that use only a normal house fan. They don't move much air and you will be much more pleased with the Canarm type fan. They are a great fan and priced very reasonable and they last forever. Paul

 

[metlmunchr]

The OSHA standard of a 100 ft/min velocity based on booth cross section is a one size fits all standard. It would cover, at the extremes of normal paint materials, anything from acrylic lacquer primers which use 200% reduction being sprayed with a conventional gun having a 30% transfer efficiency, to clear urethanes using 5% to 25%'reduction, depending on the specific product, being sprayed with an HVLP or RP gun having a 65% or better transfer efficiency.

Given the fact that the reducer is the most volatile component of sprayable paint, it's useful to compare the extremes of what the booth standard had to cover. For the lacquer primer, there's 20 oz of reducer in a 30 oz cup of paint. Using a conventional gun, 70% or 14 oz of that reducer is blown into the air. For the clear reduced 25%, there's 7.5 oz of reducer in a 30 oz cup. Using an HVLP or RP gun, 35% or 2.6 oz of reducer is blown into the air. So, the 100 fpm standard has to cover situations where you're putting reducer into the air at 5.3X the rate as compared to clear urethane reduced 25%.

Reduced base, typically with 100% reduction, would have the greatest amount of reducer going into the air among modern auto paints. 15 oz of reducer in a 30 oz cup. Assuming use of an HVLP or RP gun, 35% or 5.25 oz of reducer is blown into the air. Even so, this is barely more than 1/3 of the amount the 100 fpm standard would be handling if shooting lacquer primer with a conventional gun at 14 oz per 30 oz cup.

I've got a couple removable temporary walls in one bay of my detached garage that I set up for auto painting. The booth is 8 ft high X 13 ft wide. The 100 fpm standard would require 10,400 cfm. In reality, I'm using an axial flow fan purpose made for spray booth use, and it's handling about 4500 cfm for a velocity of about 43 fpm. Spraying epoxy, single stage, or base/clear urethanes, I get no hanging clouds of vapor while spraying. Once I stop spraying, everything clears out in 10-15 seconds max. I've painted on a hobby basis since the late 60's. Shot a lot of lacquer thru a conventional gun with nothing more than a box fan to sorta help the overspray get out the door. Since those fogs of paint and thinner never managed to explode, I don't even give a second thought to such things as the type of lights, etc now that I'm spraying paints with far less reducer thru an RP gun. I would add though that I don't press my luck by painting anywhere in the vicinity of open flames

 

[PoorUB]

I couldn't tell you how many cars, tractors or other large items I have painted in may garage with no special lighting or explosion proof anything.
As long as you have good ventilation you don't need explosion proof anything. Heck a simple furnace fan will work fine. The amount of paint vapor in the air needed to create and explosion is pretty high and you probably would not be in the room at that point.

 

[Slednut]

I may get differences of opinions here but I just built a paint booth (34x14) with 20 commercial paint booth lights i found on Craigslist from a booth that closed down. I put in 2 Canarm enclosed motor exhaust fans. (they are reasonably priced) Mine was done correctly but I wouldn't hesitate doing what your doing and feel safe painting in there. As long as you put in a big enough exhaust fan to get the correct air exchange that osha recommends. with a booth that size the fan wouldn't have to be that big. Just google paint booth air exchange and you will find a chart that recommends the required CFM for your size of booth. I have painted many things in my booth and never have any paint or fumes floating around. they are out the door immediately. I built a intake filter system that doesn't take up much room compared to the typical intake systems and if your interested I can post pics here tomorrow to give you an idea. Paul

I'd be interested in your filter system, I put up this temp booth each time I paint a project. It's small, the end walls are 11x7' and I have twelve 20x20" filters and a 7700 cfm fan.

To make my normal fan safe my 24x24' OSB duct to the outside is at an angle and I mounted the motor outside the duct and a shaft runs the fan blades inside the duct. The shaft runs through a piece of leather that is screwed to the duct.

For lighting my shop is very bright and I added sixteen 4' led lights to the outside of the booth.

Having a plastic booth I've learned static electricity causes it to attract dirt, I spend at least an hour cleaning it before I spray. I still get some dirt but after I cut and buff they're really not too much of a problem.

 

[pb57]

Here are some photos of my paint booth and intake filter system.

 

[Slednut]

Here are some photos of my paint booth and intake filter system.

That is so nice, it's got to be a pleasure to be able to paint the body, doors. hood etc at once.

 

[pb57]

Yeah it is nice, especially compared to what I used for the last 30 years. No ventilation panting inside or painting outside. Got stuff done but wow what a difference now. I have a paint booth on one side of my building and a machine shop on the other side with the middle being used for welding, prep and CNC plasma cutter. Its nice being retired. Paul

 

[Bert_]

Here are some photos of my paint booth and intake filter system.

I gotta ask, you got all the right lights but then you throw an outlet and a couple of non explosion proof fans in there?

 

[pb57]

The lights I bought off craigslist for 50 each. They came from a paint booth that closed down in Minneapolis and I got from the demo company. The fan motors are fully enclosed, but yes I have a couple outlets. I feel safe so you need not be concerned.

 

[Bert_]

Enclosed is not even close to what is required. Could have at least got some sort of belt drive blower so the motor could be outside the booth. Why bother doing a nice job with the lights if you just ignore the rest?

Any electrical inside the booth needs to be explosion proof. That means rigid threaded conduit, explosion proof fittings and boxes $$$$. There's a reason all that stuff is kept outside the booth.

 

[3rdgendslmech]

I live a charmed life, so don't do what I did. I painted numerous VW's, a couple PU's, a full size Ford van, a full size 69 Pontiac and that 58 Chevy in my avatar...in my attached 3 car garage with no special lights. I ran a furnace blower under one of the doors for exhaust. I also had the two barrel wood stove running sometimes to keep it warm in cold weather. I used a half mask with cartridges, but don't remember what they were...I got them from the chemical plant where I worked.

I'm with Yeoman, my father and I painted I cant recally how many dump trucks, heavy equipment and service trucks in a regular 1 bay shop. Had a big exhaust fan, regular flourescent lights and usually we painted with the door open a foot or 2.....we used a regular can type gun before the shop got 2 HVLP guns. And we used EMRON paint on the trucks....just used regular filter cartridge respirators.....nothing ever blew up, pops smoked a pack a day back then coupled with welding and general dust from being a heavy equipment mechanic in the field.....doctor says his lungs are as healthy as they've ever been

 

[Ronson25]

I think you overcomplicating it i wouldnt worry about the light i painted a entire 67 mustang in a 1car garage with halogen lighting and a box fan using a old can type paint gun. That was probably 20 yrs ago

 

[CraigStu]

I agree that you may be over complicating things. I have painted many fender flares and parts of cars in a plain garage w/ a stack of 2 or 3 $19 box fans in blowing out of the rear man door and the front overhead door opened may 8-10 inches wearing a replaceable filter mask. This was 20+ years ago using the old can type gun. Today an HVLP gun puts out a lot less wasted paint into the shop atmosphere. The couple of times that I painted most or all of a car, I did it just after sunrise outdoors. No wind and the dew kept the dust to a minimum. How many and how large car parts will you be painting?